This research proposal is an experimental investigation into: (1) the role of the glial cells in maintaining retinal function; (2) the ionic mechanisms of glial cell currents and their contribution to components of the electoretinogram; (3) the neuronal organization of the vertebrate retina and the different neuronal pathways reflected by glial cell currents; and (4) the information on retinal function and glial development revealed by an examination of the electroretinogram. This study will be carried out on amphibian and mammalian retina combining several experimental techniques into a single broad approach. Intracellular recording will be combined with single unit ganglion cell studies to evaluate the pathways and ionic dependencies of the neural organization underlying ganglion cell receptive fields and different glial responses. An analysis of neuronally induced changes in external potassium will be carried out with ion specific microelectrodes. The course of postnatal growth of Muller cells will be evaluated by combining intra- and extracellular studies with morphological techniques.